Stoker



July 19, 41938. w. M. scHwElcKART l sToxER F11ed sept. 15, 1954 s shee1`sshee1 1 wmf l M. :lili i l: wk l Q S Hw m, ,ww A (uw ww 11N wm MN uw HIL ww N.W.HL A NNN MN 1N k %N n E y. N. I- wm. f n/ Q .w @,7 Q N \U|\.\H Q N\ m, Q Nm w N Q @A W. M. SCHWEICKART July 19, 1938.r

' STOKER Filed sept. 15, 1954 5 Sheets-Sheena INVENTOR ATTCRN EYS July 19, 1938- l v w. M. sci-lwrslczKM-n'v 25124;.317

sToKER l Filed sept. 1s, 1934 s sheets-sheet :s

INVENT'OR .1;

. and it provides Patented July 1e, 193s PATENT CFFICE i William M. to Henry s'roxnn Schwelckart, Ramsey, N. '.T., assignor M. Brooks, New York, Tudor Gardiner, Boston, Mass.,

N. Y., William and Jacob H.

Nissley, Manheim, Pa., as trustees Application September 15, 1934, Serial No. '144,154

16 Claims.

My invention relates to center underfeed grates for solid fuel, and especially to the underfeed grates of the larger of those stokers which (being4 intended primarily for house-heating and the smaller industrial purposes) are required to operate substantially without attention. As compared with prior gratas, it increases the quantity of fuelf that can be burned per unit of time on facenter underfeed grate of given overall horizontal dimensions, it improves the distribution of the fuel to the different parts ofthe larger grates, for a more uniform distribution of the fuel and ash onto a dead plate or dead plates or other supports for fuel and ash outside the grate.

It may be used in stokers wherein the fuel is burned in accordance with ordinary practice. It is` particularly intended however' for stokers wherein the fuel is burned in accordance with the method of burning disclosed in the copending application for patent filed on or about August 24, 1934, by me and Gordon M. Peltz, Serial No. 741,216. A characteristic of this latter method, as applied to center underfeed grates and burning coals tending to cake, is the production of a column of caked coal that extends for some distance above the top of the grate orretort. As applied to this method of burning, the present invention has a further effect that it ltends to reduce the height of the caked column.

Generally speaking, I enlarge the capacity otv underfeed grates by employing upwardly extending walls of sinuous form, at least in those regions that are pierced with the ports which admit combustion air to the fuel, thus increasing the exposure of the fuel tothe incoming air and thereby permitting the feed of both air and fuel at greater rates than heretofore. I contemplate that lthe walls will stand more nearly vertically than horizontally, and be of about equal heights, at least usually. In effect, each sinuosity or upwardly extending channel provided by the sinuous form'of the wall may be more or less like an individual small grate or retort, the whole converging to a common feeding conveyor at or beneath the roots of the channels and the fuel contents of thechannels being more or less joined together and thus constituting more or less of a single entity. For grates of thelarger sizes at least, these individual small grates or retorts are usually arranged in a line or lines. To secure the desired distribution of the fuelwithin or on an elongated grate, metering means may be employed to aifect the distribution of the fuel entering the grate, for examle an obstruction or '5 for feeding air to the space (ci. 11o-45) obstructions to the flow of fuel along a common fuel-feed-passageway at the bottom of the grate, preferably of the kind described hereinafter and this can be supplemented by a conveyor located in the grate and preferably lengthwise, varying in 5 capacity as hereinafter described. To improve the distribution of the fuel and ash outside the grate or retort, each channel may be more or less laid over in such amanner as to direct its contents toward some more or less individual 10 locality outside the grate. As applied to the method of burning disclosed in the said co-pending application, each channel is laid over toward some more or less individual locality outside the-` grate and its walls around the fuel mass rising through it to incline the caked column toward this locality and thus cause the topl 'of the column to break off at a lower level than it would were the column directed straight upwardly.

These and other matters concerned with my invention appear in the two forms of it illustrated in the accompanying drawings, in'which:` Fig. 1 is a sectionalized elevation illustrating a grate of my invention employed in a conventional my invention to a conventional form of Stoker.

In general, the stoker comprises the grate I (the sinuous rectangular grate of Figs. 2 and 3 here being illustrated),` a fuel conduit 2 and screw conveyor 3 therein to feed fuel to the bottom of the grate? and through the center fuel inlet port or ports and thence over the grate, an air conduit 4 and blower 6 underneath the grate whence this combustion air passes through the air ports 1 in the grate walls and an electric 45 motor 8 for driving the blower 5 and conveyor 3; as is customary, the impeller of the blower 5 may be mounted directly on the motor shaft while the conveyor 3 is driven from the motor through a speed reducing gearing 9 and such supplemental 5o drives I0 as may be necessary or convenient. A dead plate Il encircles the grate I for the collection of the ash, and brick work I2 both completes the enclosure of the air chamber 6 and supports the dead plate II. -It will be understood 55 are extended sufilciently 15 force this fuel upwardly of course that my invention is not limited to either the mechanism or the form of stoker illustrated in .'Fig. 1, the showing here being entirely representative.

For convenience of construction, the grate of Figs. 2 and 3 is composed of three sections, the

lower section I6, an intermediate plate-like section I1 (the inner and outer rims of which are joinedby arms to permit the upward ow of combustion air therethrough) and the upper section I8, which is provided with the combustion air ports 1. The intermediate and upper sections |1 and I8 are secured together as by various bolts I9, piercing horizontal arms of these members; likewise` the lower and intermediate sections I6, I1 may be fastened together by bolts piercing arms of the intermediate member I1 and ears 20 of the lower section I6 (Fig. 4). form no part of the present invention. The important thing, first, is that, regardless of whether the grate is an integral or composite member, its upwardly extending wall, which provides or substantially encloses a passageway for the upward flow of fuel, is sinuous in form, as will be observed particularly in Fig. 3; the grate there illustrated being provided with two bays or upwardly extending channels 2| and 22 in one of the long side walls of the grate and two other bays or upwardly extending channels 23 and 24 in its opposite side wall. The side walls 25 of each bay or channel are of considerable width, whereby each` channel is of material horizontal depth (Figs. 3 and 4) the width of these side walls apprximating the width or distance between them and the width of the respective outer walls 28 and 21; that is to say, the widths of the side walls and the width or distance between opposing side walls (which is substantially equal to and represented by widths of the outer walls) are of the same general order; for example, in the grate of Figs. 1 to 4 (see Fig. 3) the width of each side wall 25, near the top of the grate, is about twothirds or three-quarters the width of each outer wall' 21 and about one-half or two-thirds the width of each outer wall 26. The enclosing or upwardly extending wall is sinuous in form externally as well as internally and thus provides passages for combustion air between side walls 25 of adjacent channels, and perforations 1 for the passage .of combustion air are provided in the side walls 25 of the channels, and preferably in the outer walls 26 and 21 of the channels. Usually I make the encompassing wall at the outwardly facing portions of the the outer walls 26 and as high as the tops of channel therefore, it provides more or less 21, at least substantially the side walls 25. Each will be observed (Fig. 3), of an individual grate open at its lower end to the common fuel feeding means, e. g. the fuel conveyor 3, but the sides of the channels are open to each other so that the fuel contents of thel channels join and constitute a single entity. 'I'he channels or spaces for the upward ilow of fuel, are so constructed that the axes of the various paths of fuel travel through them are differently 2| is so constructed that (for example a caked column of) fuel rising through it is inclined generally toward the upper and left-hand corner of the picture (Fig. 3) while fuel and ash rising through the adjacent channel 23 is inclined in the opposite direction, i. e. toward the bottom of the picture; also channel 22 inclines its contents to- Ward the upper part of the picture land channel 24 toward the lower side. Thus it is evident that These matters channels, i. e. the tops of inclined. Thus the channel the grate tends to distribute its ash and fuelv discharge onto the encompassing dead plate I| more or less uniformly throughout the circumference of the dead plate. Preferably, at least for grates to burn a considerable quantity of coal per hour, these channels or spaces for the upward flow of fuel are arranged more or less in a line along the fuel conveyor, as illustrated in Figs. 2 and 3, or along the line of said conveyor means extended, and the adjacent uchannels or spaces have fuelpath-axes inclined toward opposite sides, as described with respect to the grate of Figs. 2, 3 and 4. Preferably this inclination of the fuel paths is obtained by inclining the channels themselves, i. e. the upwardly extending center lines of the individual channels, and carrying the walls of the individual channels sufllciently around the fuel Within the respective channel to forcev the upwardly rising fuel columns in the desired directions. For example (referring particularly to Figs. 3 and 4), all these wallsirise more nearly vertically than horizontally, but the outer wall 26 of the channel 24 may be inclined in the direction the fuel mass is desired to go, while the opposite wall 21 of the same channell rises substantially vertically to substantially the same height as the wall 26, thus throwing the upwardly extending center line of this channel 24 distinctly to the left in Fig. 4, the desired direction of discharge for this particular channel 24. Accordingly (referring to Fig. 3), the wall 21 oi' the channel'2 2 (which wall is at the opposite side of the fuel conveyor 3 and hence the horizontal passageway for fuel at the bottom of the grate from the wall 21 of the channel 24) rises vertically while its respectively opposing outer wall 26 is inclined toward the upper side of Fig. 3 (to the right in Fig. 4).

In order that the various channels or spaces for the upward flow of fuel may receive the proper amounts of fuel respectively, usually I -extend the fuel conveyor '(for examplel 3) underneath substantially all of the lchannels or spaces, I obstruct the free flow of fuel from space to space, and also I progressively decrease the capacity of the conveyor as it extends from one space to another; to the extent that the flow is obstructed and the capacity of the conveyor is reduced from one space to another, the fuel is necessarily fed into the first of these spaces. Thus referring to Fig. 2 for example: The fuel conveyor screw 3 extends along the bottom of substantially the whole grate. It enters the bottom of the channel 2| with substantially the same diameter and pitch of thread as elsewhere toward the chamber I2 from which the conveyortakes the fuel, but between point 3| and point 32 both the diameter of the screw 'and the pitch of the thread are less than the diameter and pitch to the left of the point 3|, the diilerence representing, generally speaking, the part of the fuel intended to be delivered into the channel or space 2|. Again, the diameter and pitch between points 32 'and 33 are less than the diameter and pitch between points 3| and 32, the diiference representing, generally speaking, the part of the fuel to be delivered to the channel 23. Also at point 3 3 the diameter and pitch are again reduced to dis- P tribute the remainder of the fuel between the channels 22 and 24. Cooperating with the conveyor are the obstructions 34 to the free ilow of fuel along the bottom of the grate. These may be integral parts of the grate; each extends more or less transversely of and part way across the bottom fuel passageway, say adjacent one of the points 3l, 32, 33, so as to hold back some of the fuel entrained by the conveyor, and preferably each has the form of a guide to direct this fuel more or less upwardly into the respective part of the grate. Preferably each is a bridge 34 spanning the bottom passageway, each bridge being pierced for the passage of the fuel conveyor through it and each being sloped more or less upwardly in the direction of fuel movement, as ,indicated .at 35, to form substantially an upwardly opening elbow for directing upwardly the fuel engaged by it. Usually I make each hole in a bridge only about large enough to contain the conveyor (i. e., the holes differ in size in`\` the grate illustrated). Other ways of varying the capacity of a screw are known of course; for example, the shaft within the thread may be varied; also the thickness of the thread can be varied. Preferably the fuel-guiding wall of each bridge-elbow 34 extends for some distance above the conveyor, as illustrated in Fig. 2. It will be apparent that this method of metering or distributing the fuel over the grate is not limited to sinuous grates but is applicable to all elongated grates.

As before indicated, my present invention is particularly well adapted for use with the method of burning vdisclosed in the co-pending application for U. S. patent mentioned above. To this end combustion air ports 'l are arranged in a single horizontal plane, and the blower can be assumed to develop sufficient pressure to provide the requisite air velocity and the fuel conveyor 3 to feed Ifuel at the proper related rate to cause the fuel to burn in accordance with this method. As a result, with caking coals,\a burning column or columns of fuel rise from the various channels or spaces 2l to 24, this or these tending to separate however into four: distinct units, of which adjacent columns inclinein opposite directions. As a result ofthe inclination, the tops of these columns break and fall toward t-he dead plate II before the column reaches the height to which it would extend if it were not inclined; and the inclination of the various columns in oppositedirections distributes the aggregates thatbreak from the columns and the ash more uniformly over the dead plate I I than were the differing inclinations omitted.

Figures 5 and 6 illustrate another sinuous grate, or rather the application of the sinuous idea to a circular grate. The combustion air chamber or passage 40 and airports 4l will be recognized.

' As will be observed from the plan view, the grate,

while generally circular, is sinuous in form internally and thereby provided with sixbays, spaces or upwardly opening channels 43 in its upwardly and outwardly flaring wall, and in accordance with the broader aspect of my present invention, the combustion air ports 4I pierce the grate in the localitybf these channels, some'of the ports being in opposing side walls 44 of each channel and other of lthese ports being in the outer walls 45 of the channels. As with respect to Figs. l to 4, the upwardly extending wall of the grate'of Figs. 5 and 6 is sinuous externally as well as internally, and thus provides passages for combustion air between the side walls 44. of adjacent channels 43,y these passages leading combustion air to the ports 4I in those side walls (Fig. 5); as before also, the side walls 44 lare of considerable width, whereby each channel 43 is of material horizontal depth, the greatest widths of these side walls (i. e. their widthsnear the top of the grate) approximating the width between the members of each pair of side walls and the widths of the outer walls 45 (Fig. 5); that is to say, the greatest widths of the side and outer walls are of the same general order; for example, in the present grate the greatest width of each side wall 44 is about one-half the width of each outer wall 45 (Fig. 5). It will be understood, too, that the fuel is fed upwardly through these grates of Figs. 5 and 6 through a center inlet port, e. g.'from the usual conduit 46. These Figs. 5 and 6 being intended to illustrate a simpler form of the sinuous construction, and the sinuous construction as applied to a more or less circular grate, the foregoing description will suflice.

It will be understood of course that my invention is ,not limited to the details of operation and construction above described, except as-appears hereinafter in the claims.

I claim:

1. An underfeed grate comprising an upwardly extending wall substantially encompassing a passageway for the upward feed of fuel from below and of sinuous form to provide a plurality of channels for the fuel extending upwardly, said passageway being open at its upper and lower ends, and said wall being perforated for the passage of combustion air to the fuel contained within it, characterized lby the fact that portions of said wall forming Walls of adjacent channels are sloped in different directions whereby the fuel flows in different directions in each two adjacent channels.

2. The subject matter of claim 1, further characterized by the fact that saidA encompassing Wall is perforated for the passage of 'combustion air to the fuel both at the sides and at the outer surfaces of thechannels.

3. A center underfeed grate having a substantially central fuel inlet port for the upward feed of fuel therethrough and an upwardly rising wall substantially encompassing said inlet port and provided with perforations for the passage of combustion air to the ,fuel on the grate. said upwardly rising wall being sinuous in form to provide a plurality of channels in the region of said perforations and there being perforations,

4extending wall substantially encompassing a passageway for the upward feed of fuel from below and of sinuous form to provide a plurality of channels for -the fuel extending upwardly, said encompassing wall providing each channel with` side walls of considerable .width whereby each channel is of material horizontal depth, approximating its width between theside walls, and being perforated at said side walls of the channels for the passage of combustion air-to the fuel contained within the encompassing wall, and the encompassing wall at the outwardly facing portions of the channels being at least substantially as high as its top at the said side walls of the channels.

5. An underfeed grate comprising an upwardly extending wall substantially encompassing a passageway for the upwardfeed of fuel from below and of sinuous form 'internally to provide a plurality of channels for the fuel Aextending upwardly, said encompassing wall extending more nearly vertically upwardly than horizontally, and providing each channel with an outer wall and with side walls of considerable width, whereby each channel is of material horizontal depth, approximating its width between the side walls, and also being of sinuous form externally to provide passages for combustion air between the side walls of adjacent channels, and being perforated, both at said outer walls and at said side walls of the channels, for the passage of combustion air to the fuel contained within it.

6. An underfeed grate provided Awith a substantially horizontal passageway for fuel near its bottom, and having upwardly rising wal-ls at opposite sides of said passageway and upwardly rising walls extending substantially transversely of said passageway to provide, and dividing said grate into, a plurality of channels for the upward ilow of fuel, perforations for the passage of combustion air to the fuel being provided in said walls, and for each channel the upper ends of those walls which are at opposite sides of said passageway being located one nearer than the other to the vertical plane containing the axis of said passageway, and with respect to adjacent channels the wall of one channel which is nearer said plane being cn the opposite side of said plane from the wall -of the other channel which is nearer said plane.

7. The subject matterI of claim 6, characterized by the fact that adjacent channels open into each other.

8. The subject matter of claim 6, further characterized by the fact that a fuel conveyor is provided in said passageway, said conveyor extending beneath substantially all said channels.

9. The subject matter of claim 6, further characterized by the fact that a fuel conveyor is provided in said passageway. said conveyor extending beneath substantially all said channels, and having progressively lesser capacity as it extends from one channel to another.

10. The subject, matter of claim 6, characterized by the fact that adjacent channels open into each other, and means are provided beneath substantially each of said channels to direct some of the fuel from said passageway to each of said channels.

11. The subject matter of claim 6, characterized bythe fact that said channels are substantially rectangular horizontally.

12. The subject matter of claim 6, adjacent channels opening into each other, further characterized by the fact that a conveyor comprising a screw thread on a shaft is provided in said passageway and extends beneath substantially all said channels, the distance between the shaft and the circumference of the thread decreasing as said conveyor passes from one channel to the next and guidesbeing provided adjacent the conveyor, at each change in said distance, to direct fuel into the channels. y 13. The subject matter of claim 6, characterized by the fact that a fuel conveyor is provided in said passageway, said conveyor extending bea plurality of channels for the upward flow of fuel, perforations for the passage of combustion air to the fuel being provided in said wall portions, and for each channel the upper ends of those wall portions which are at opposite sides of said passageway being located one nearer than the other to the vertical plane containing the .axis of said passageway, and with respect to adjacent channels the wall portion of one space which is nearer said plane being on the opposite side of said plane from the wall portion of the other space which is nearer said plane, characterized by the fact that between each pair of adjacent channels for the upward ow of coal, means are provided extending substantially across said passageway toA direct the fuel into columns rising upwardly through said channels, each of said means providing a passage for the movement of fuel along said passageway, and each succeeding passage being smaller than the passage in advance of it.

15. Anv elongated underfeed grate having a passage way for the supply of fuel extending lengthwise of the grate near its bottom, characterized by the fact that means are provided extending substantially across said passage way, at a plurality of points spaced longitudinally of the passage way, to direct the fuel into columns rising upwardly from said passageway, each of said means providing a passage for the movement of fuel along saldlpassage Way, and each succeedingpassage vbeing smaller than the passage in advance of it. y

1.6. The subject matter of claim 15, further characterized by the fact that a fuel conveyor is provided in said passage way extending through said passages in said fuel directing means, the' capacity of said conveyor at and beyond each succeeding passage being less than its-capacity at the passage respectively in advance of it.

WIILIAM M. SCHWEICKART. 

